Lance for heating or ceramic welding

ABSTRACT

Apparatus and process for one of flame treatment or ceramic welding, the apparatus including a single tubular lance having a tip end, a butt end, and a head portion with a central main bore provided at the tip end so that ceramic welding materials comprised of particulate material containing oxidizable particles and combustion-supporting carrier gas are introduced at the butt end, pass through the main bore and emerge at the tip end during ceramic welding; wherein the head portion further comprises at least one conduit to convey a mixture of a fuel gas and a combustion-supporting gas, each of the at least one conduit having an orifice at the tip end of the single tubular lance and being provided with a portion for introduction of fuel gas and a portion for introduction of combustion-supporting gas so that fuel gas and combustion-supporting gas introduced at the butt end combine in the at least one conduit and emerge to form a flame at the tip end of the at least one conduit during flame treatment, and wherein the head portion is formed in two parts including an inner block including the central main bore, the conduits for fuel gas and combustion-supporting gas, and respective outlet orifices of the central main bore and at least one conduit, and an outer block including supply passageways to the inner block from respective supply tubes for particulate material and combustion-supporting carrier gas and for fuel gas and combustion-supporting gas.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to lance apparatus employed for either heatingpurposes or for ceramic welding purposes, such as providing a heatingflame or conveying sand or like solid particulate material in acombustion-supporting carrier gas. In particular the invention relatesto the tip configuration of a lance used alternatively to provide aflame or to effect ceramic welding. The invention also covers a processusing the said lance apparatus.

2. Description of the Related Art

In ceramic welding, a mixture of solid refractory particles and solidcombustible fuel particles of a metal or semi-metal such as aluminium orsilicon is projected in a carrier gas stream, typically of oxygen,against a surface. The fuel particles react with oxygen in a highlyexothermic manner to form a refractory oxide, sufficient heat beingreleased against the surface to melt at least the surface of therefractory particles and form a coherent refractory mass. Such “ceramicwelding” is described in Glaverbel GB patent specifications 1,330,894and 2,170,191.

Ceramic welding can be employed for forming a refractory article, forexample, a block having a particular shape, but it is most widely usedfor forming coatings or for repairing bricks or walls constructed ofrefractory oxide materials. It is particularly useful for repairing orreinforcing existing refractory furnace structures, for example, furnacewalls in glassmaking or coke ovens, especially since the repair can beeffected while the furnace is in operation.

In order to reach the repair zone, which may be several meters away fromthe operator, the lances tend to be long and to have much ancillaryequipment such as flexible supply lines for the gases and particulatematerial. They also typically include a water-cooled jacket, withassociated supply lines for the cooling water. Thus the lances can bevery heavy and cumbersome to manipulate, requiring in some instances theprovision of special scaffolding and associated lifting equipment to putthem into the operating position.

In effecting the repair it is commonly necessary to prepare the surfaceto be repaired, for example to remove loose or foreign material in orderto provide a sound base to which the repair mass can adhere. In someinstances the repair surface has been treated by introducing a comburentgas into the zone to be repaired to burn off unwanted deposits.

Lances for use in such purposes as cleaning are long established.EP-A-0069286 relates to a lance for flame spraying a metal refiningvessel including a furnace bottom cleaning device which feeds oxygen tothe required point of use. Burners are also known to clean refractorysurfaces.

Given the refractory nature of the base it is desirable to employ anintense cleaning flame which can if necessary quickly melt part of thesurface to be repaired, leaving a fresh surface on which to effect therepair. Particularly in the case of glassmaking furnaces, a vitreousphase may be present as a residue of molten glass, as an exuded bondingphase in the refractory material or as a result of deposition ofrefractory dust from the vitrifiable material mixture introduced intothe glass melting tank. A vitreous phase is especially likely to befound in refractory blocks at or from the level of the molten glass linein a glassmaking furnace. These blocks are typically of high quality Zacrefractories.

A conventional repair of damaged or worn refractory walls within afurnace such as a glass furnace by means of first a flame treatment ofthe wall surface followed by spraying a ceramic welding powder mixturetends to involve much manipulation of the burner and of the ceramicwelding lance. The steps of removing the burner and inserting anddirecting the ceramic welding lance to the flame-treated area can bedifficult and time-consuming. The resultant delays, which may typicallybe 20 to 60 minutes, are also long enough for a vitreous phase to beginto reappear on the wall surface. Moreover the hardening effect, whichcreates a refractory structure which exudes less, is lost.

GB patent specification 2237803 relates to a ceramic welding nozzlewhich has a central bore for weld material in a gaseous fluid, such asair, and combustion means adjacent to the nozzle outlet for theinjection into the gaseous fluid of a combustible fluid, such aspropane, butane or acetylene. The combustion means is primarily employedto assist the weld formation by heating the weld particles and thesubstrate refractory. The combustible fluid mixes with the gaseous fluidfrom the central bore and reacts with the oxygen therein to form aheating flame in the vicinity of the repair zone. The flame can be usedsimply for preheating the repair surface but the defined nozzle does notlend itself to the formation of an intense flame, the combustible fluidbeing introduced into a gaseous fluid from the single central bore andthus being dispersed over a relatively wide area. This system does notpermit and does not envisage scouring of the surface prior to therepair.

It is an object of the present invention to provide a lance which has aninbuilt capability to deliver an intense flame independently of itsfunction for ceramic welding or like purposes.

SUMMARY OF THE INVENTION

According to the invention there is provided apparatus for alternativelycreating flame or effecting ceramic welding, which comprises a singletubular lance having a tip end and a butt end and having a head portionwith a central main bore at the tip end, whereby ceramic weldingmaterials comprising particulate material containing oxidisableparticles and combustion-supporting carrier gas are introduced at thebutt end, pass through the main bore and emerge at the tip,characterised in that the head portion (10+20) further comprises atleast one conduit (28) to convey a mixture of a fuel gas and acombustion-supporting gas, each such conduit (28) having an orifice (29)at the tip of lance and being provided with a portion (28 a) for theintroduction of fuel gas and a portion (28 b) for the introduction ofcombustion-supporting gas, whereby fuel gas and combustion-supportinggas introduced at the butt end combine in the conduit (28) and emerge toform a flame at the tip end of the or each conduit (28) and emerge toform a flame at the tip end of the or each conduit (28) and in that thehead portion is formed in two parts, an inner block (20) including themain bore (23) and the (28) for fuel gas and combustion-supporting gasand including the outlet orifices of the said bore and conduit(s) (29),and an outer block (10) including supply passageways to the inner blockfrom respective supply tubes for particulate material and carrier gas(13) and for fuel gas and combustion-supporting gas (15, 16).

The invention also provides a process for alternatively creating flameor effecting ceramic welding, using a single tubular lance having a tipend and a butt end and having a head portion with a central main bore atthe tip end, whereby ceramic welding materials comprising particulatematerial containing oxidisable particles and combustion-supportingcarrier gas are introduced at the butt end pass through the main boreand emerge at the tip, characterised in that a mixture of a fuel gas anda combustion-supporting gas is conveyed through at least one conduit inthe head portion other than the main bore, the head portion furthercomprises at least one conduit having an orifice at the tip of thelance, whereby fuel gas and combustion-supporting gas separatelyintroduced at the butt end combine in the conduit and emerge to form aflame at the tip end of the or each conduit.

By separating the flame-forming gases from the main stream gases theinvention provides homogeneous mixing of these gases in the optimumproportions for the required flame allows the flame formation to befully independent of the ceramic welding function required for thestream through the main bore. Thus the flame can first be employed toclean or otherwise treat a target surface and secondly the main borestream can be commenced immediately for its intended ceramic weldingpurpose. Problems of manipulating the lance or different lances betweenthe two different purposes are thus eliminated and the second purposecan start before any loss of heat occurs from the target surface.

The invention is also well suited to the use of high flame temperaturefuel gases in easily controlled proportions to obtain the desired flameintensity. Acetylene and acetylene mixtures such as tetrene™ aregenerally preferred since they allow flame temperatures well in excessof 2000° C. to be readily achieved. Other gases such as propane may alsobe suitable for particular applications. The combustion-supporting gasis preferably oxygen as such.

For most purposes it is preferred that the main bore is substantiallyaligned with the central axis of the head portion and that a pluralityof conduits for fuel gas and combustion-supporting gas are disposedaround the main bore. The conduits should preferably be evenlydistributed around the main bore and they should preferably besufficient in number to provide a continuous annular flame, therebyproviding heat across the full area to be treated. For a ceramic weldinglance of conventional size the number of conduits to achieve this istypically 12. The conduits should preferably be parallel to each otherbut may be slightly divergent from each other, for example at an angleof 2-3° from the head axis. The resulting outward alignment of theformed flame assists in moving any molten material away from thetreatment area. The removal of such molten material is also facilitatedby the use of an intense high pressure flame as permitted by theinvention.

Each of the plurality of conduits for fuel gas and combustion-supportinggas is preferably a branched conduit, with two feed branches combiningto form a single outlet. The feed branches are supplied separately withfuel gas and combustion-supporting gas from the butt end of the lanceand the said gases combine within the head to emerge fully mixed at theoutlet orifice.

The preferred internal diameter of the conduits at the tip end of thelance depends upon the chosen fuel gas. For high flame temperature gasesthe diameter is preferably in the range 1.5 to 3 mm. For acetylene andtetrene the diameter is typically in the range 1.5 to 2.5 mm and forpropane is typically in the range 2.0 to 3.0 mm.

The preferred pressure of the fuel gas/combustion-supporting gas mixtureis dependent on the burner configuration and upon the nature of thesubstrate to be treated. It is generally measured, and can be readilyadjusted, at the respective supply cylinders for the fuel gas andcombustion-supporting gas. Such adjustment also permits the choice of apressure which keeps the flame attached to the lance tip. When usingindustrially pure oxygen as the combustion-supporting gas the regulatedsupply pressure from the cylinder is typically about 4.0 to 5.0 bar (0.4to 0.5 MPa). The fuel gas is typically supplied at a lower pressure, forexample about 2.0 to 2.5 bar (0.2 to 0.25 MPa) and at a lesser rate thanthe combustion-supporting gas, such that in a branched supply conduit asdescribed above the combustion-supporting gas exerts an aspiratingeffect on the fuel gas at the point of mixing.

For industrial applications, the burner setting can conveniently beeffected outside the treatment zone on a trial piece, for example on asample of a refractory material to be cleaned and repaired. In thisexample the proper setting (and from this the proper temperature) isdetermined by when melting of the refractory surface is observed.

For convenience of construction the head portion of the lance ispreferably formed in two parts: an inner block including the main boreand the conduits for fuel gas and combustion-supporting gas andincluding the outlet orifices of the said bore and conduits, and anouter block including supply passageways to the inner block fromrespective supply tubes for particulate material and carrier gas and forfuel gas and combustion-supporting gas.

In a preferred embodiment the inner block of the head portion is locatedand held in position by a combination of internal threads in at leastpart of the outer block and external threads on at least part of theinner block.

Conveniently a shaped annular groove is provided in the outer surface ofthe inner block so as to form in association with the adjacent innersurface of the outer block an annular distribution chamber for fuel gas.Similarly it is convenient to provide a shaped annular groove in theouter surface of the inner block so as to form in association with theadjacent inner surface of the outer block an annular distributionchamber for combustion-supporting gas.

The lance is provided with a supply tube for the suspension of particlesin a carrier gas stream, a supply tube for fuel gas and a supply tubefor combustion-supporting gas. These tubes are conveniently encircledwithin a protective tube. This protective tube is not essential for theinvention but constitutes a useful protection against gas-water mixture,for example in the event of leaks due to the rupture of solder in thegas supply lines. The protective tube ensures the rigidity of the lancebut with an increase in its weight.

For many applications the lance preferably includes an external coolingjacket through which a fluid coolant such as water can be passed. Thejacket typically comprises two tubes coaxial with each other and withthe lance and with an opening or openings between the tubes at the tipend enabling the supply of coolant from the butt end though the annularspace between the lance and the inner jacket tube and return of thecoolant through the annular space between the inner and outer jackettubes.

Lances employed for ceramic welding and including the above-describedembodiments have no special requirements for compositions and feedratesof powder and carrier gas, being fully usable with the normally employedtypes and volumes of feed materials.

A particular advantage of the process according to the invention is thatafter a flame formed by combustion of the fuel gas is applied to asurface to be treated to achieve a desired effect thereon the flametreatment can be stopped and immediately replaced by a stream ofparticles in a carrier gas stream directed to the surface to be treated.As a result of the use of the flame, the surface of a refractorysubstrate for repair is completely renewed and has the same quenchstructure as a new block of the same material. The ceramic weld massapplied immediately thereafter through the main bore is fully compatiblewith the refractory substrate and its adhesion to the substrate isespecially strong.

BRIEF DESCRIPTION OF THE INVENTION

The invention is further described below with reference to theaccompanying drawings, in which,

FIG. 1 is a sectional view of the end portion of a lance according tothe invention (the section being taken along line B—B of the followingFIG. 2). The lance is of a type suitable for ceramic welding.

FIG. 2 is an end view of the tip of the lance shown in FIG. 1, the viewbeing taken from position A—A on FIG. 1

FIG. 3 is a sectional view of the end portion of the lance shown inFIGS. 1 and 2, the section being taken along line C—C of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The illustrated lance has a supply tube 3 for a suspension of ceramicwelding powder in a carrier gas stream, a supply tube 5 for fuel gas anda supply tube 6 for oxygen. A protective tube 8 encircles the tubes 3, 5and 6. The powder suspension, fuel gas and oxygen are all conveyed inthe direction indicated by the central arrow.

The tubes 3, 5, 6 and 8 are attached to and terminate in an outer hollowblock 10 which has a generally frusto-conical portion 11 and a generallycylindrical portion 12. The block 10 has internal conduits 13, 15 and 16which are shaped at its upstream end to be aligned with the ends of thetubes 3, 5 and 6 respectively and to provide conduits through the block10 for powder/carrier gas, fuel gas and oxygen respectively.

An inner distributor block 20 is located within the outer hollow block10, being held in place by complementary threads 14 on the respectiveblocks. The block 20 has an axial bore 23 aligned with the upstream endof the conduit 13 of block 10. At its downstream end the bore 23includes internal threads 24 to receive an optional externally-threadedtubular insert to reduce the internal tip diameter of the bore 23 to thedimension best suited to the specific repair task. The said internal tipdiameter is typically in the range 1.2 to 2 mm.

A shaped annular groove 25 in the outer surface of the block 20 forms inassociation with the adjacent inner surface of the block 10 an annulardistribution chamber for fuel gas. The conduit 15 passes through theblock 10 at an angle to its axis and terminates at its inner surfacewithin the said annular distribution chamber.

Similarly a shaped annular groove 26 in the outer surface of the block20 forms in association with the adjacent inner surface of the block 10an annular distribution chamber for oxygen, the conduit 16 passingthrough the block 10 at an angle to its axis and terminating at itsinner surface within the said chamber.

Branched bores (conduits) 28 of 2 mm internal diameter lead from theannular grooves 25 and 26 through the block 20, emerging at orifices 29in its downstream face. The bores 28 comprise a long straight portionleading from the annular groove 26 to an orifice 29 and a short sidebranch 28 a connecting from the annular groove 25. The portion of eachbore 28 upstream of the side arm 28 is indicated by the reference number28 b. There are twelve such branched bores 28 and orifices 29 in theillustrated version.

In the primary intended use of the lance for ceramic welding repairoperations, fuel gas and oxygen are initially introduced through tubes 5and 6. The oxygen passes through angled conduit 16 to the annular groove26 and then through the twelve bores 28 and orifices 29. The fuel gaspasses through angled conduit 15 to the annular groove 25 and is drawninto the oxygen stream in the bores 28 through the side branches 28 a.Thus the side branches 28 a carry just fuel gas and the portions 28 bcarry just oxygen, such that the fuel gas and oxygen do not combinebefore they meet at the junction of branches 28 a and portions 28 b. Aflame is created from the so-formed fuel gas/oxygen mixture emergingfrom each of the orifices 29, providing in combination a generallyannular-shaped cleaning flame to be played on the surface to berepaired.

When the flame has had its desired effect on the repair surface thesupplies of fuel gas and oxygen to tubes 5 and 6 are stopped. A streamof ceramic welding powder comprising refractory particles and solid fuelparticles in an oxygen carrier gas stream is then introduced through thetube 3, conduit 13 and bore 23 to impinge upon the repair surface, wherethe solid fuel ignites to form a coherent and adherent repair mass.

A water jacket formed of an outer tube 31 and an inner tube 32 isdisposed around the block 20 and tube 8. The ends of the tubes 31 and 32are closed off by an annular end plate 33. In operation of the lance,cooling water is introduced in the direction shown by the twointermediate arrows in FIG. 1 into the annular space between the tubes32 and 8, then through the annular end space between the tube 31 andblock 10 and thence back out of the lance through the annular spacebetween jacket tubes 31 and 32, as indicated by the outer arrows in FIG.1.

In a trial employing apparatus as described above oxygen was supplied tothe lance through the conduits 28 at a pressure of 4.5 bar (0.45 MPa)and propane fuel gas was supplied through the said conduits 28 at apressure of 2.0 bar (0.2 MPa). The resulting flame was applied to AZSelectrocast blocks to melt the surface and remove a surface layer,including a vitreous phase therefrom. The oxygen and propane supplieswere then stopped and a ceramic welding powder suspended in oxygen ascarrier gas was immediately supplied through the bore 23 to impinge onthe refractory surface. A high quality adherent repair mass was formedon the refractory block.

What is claimed is:
 1. Apparatus for one of flame treatment or ceramicwelding, comprising: a single tubular lance having a tip end, a buttend, and a head portion with a central main bore provided at the tip endso that ceramic welding materials comprised of particulate materialcontaining oxidizable particles and combustion-supporting carrier gasare introduced at the butt end, pass through the main bore and emerge atthe tip end during ceramic welding; wherein the head portion furthercomprises at least one conduit to convey a mixture of a fuel gas and acombustion-supporting gas, each of the at least one conduit having anorifice at the tip end of the single tubular lance and being providedwith a portion for introduction of fuel gas and a portion forintroduction of combustion-supporting gas so that fuel gas andcombustion-supporting gas introduced at the butt end combine in the atleast one conduit and emerge to form a flame at the tip end of the atleast one conduit during flame treatment, and wherein the head portionis formed in two parts, an inner block including the central main bore,the conduits for fuel gas and combustion-supporting gas, and respectiveoutlet orifices of the central main bore and at least one conduit, andan outer block including supply passageways to the inner block fromrespective supply tubes for particulate material andcombustion-supporting carrier gas and for fuel gas andcombustion-supporting gas.
 2. The apparatus as claimed in claim 1,wherein the head portion has a central axis, wherein the central mainbore is substantially aligned with the central axis of the head portion,and wherein a plurality of conduits for fuel gas andcombustion-supporting gas are disposed around the central main bore. 3.The apparatus as claimed in claim 2, wherein the plurality of conduitsare evenly distributed around the central main bore.
 4. The apparatus asclaimed in claim 2, wherein the plurality of conduits are present in anumber sufficient to provide a continuous annular flame.
 5. Theapparatus as claimed in claim 2, wherein each of the plurality ofconduits is a branched conduit and wherein two branched conduitscombining to form a single outlet.
 6. The apparatus as claimed in claim2, wherein each of the plurality of conduits has an internal diameter atthe tip end of the single tubular lance which ranges from 1.5 to 3.0 mm.7. The apparatus as claimed in claim 1, wherein at least a portion ofthe outer block is provided with internal threads, wherein at least aportion of the inner block is provided with external threads, andwherein the inner block is located and held in position by a combinationof the internal threads provided in the outer block and the externalthreads provided on the inner block.
 8. The apparatus as claimed inclaim 1, wherein an annular distribution chamber for fuel gas is formedby a shaped annular groove provided in the outer surface of the innerblock in association with an adjacent inner surface of the outer block.9. The apparatus as claimed in claim 1, wherein an annular distributionchamber for combustion-supporting gas is formed by a shaped annulargroove provided in the outer surface of the inner block in associationwith an adjacent inner surface of the outer block.
 10. The apparatus asclaimed in claim 1, wherein the single tubular lance further comprisesan external cooling jacket through which a fluid coolant may be passed.11. The apparatus as claimed in claim 10, wherein the fluid coolant iswater.
 12. Apparatus for one of flame treatment or ceramic welding,comprising: a single tubular lance having a tip end, a butt end, and ahead portion with a central main bore provided at the tip end so thatceramic welding materials comprised of particulate material containingoxidizable particles and combustion-supporting carrier gas areintroduced at the butt end, pass through the main bore and emerge at thetip end during ceramic welding; wherein the single tubular lanceincludes a supply tube for a suspension of particles in a carrier gasstream, a supply tube for fuel gas, and a supply tube forcombustion-supporting-gas, and wherein a protective tube is providedwhich encircles the supply tubes in combination, wherein the headportion further comprises at least one conduit to convey a mixture of afuel gas and a combustion-supporting gas, each of the at least oneconduit having an orifice at the tip end of the single tubular lance andbeing provided with a portion for introduction of fuel gas and a portionfor introduction of combustion-supporting gas so that fuel gas andcombustion-supporting gas introduced at the butt end combine in the atleast one conduit and emerge to form a flame at the tip end of the atleast one conduit during flame treatment, and wherein the head portionis formed in two parts, an inner block including the central main bore,conduits for fuel gas and combustion-supporting gas, and respectiveoutlet orifices of the central main bore and the at least one conduit,and an outer block including supply passageways to the inner block fromrespective supply tubes for particulate material andcombustion-supporting carrier gas and for fuel gas andcombustion-supporting gas.
 13. A process for one of flame treatment orceramic welding, comprising: providing a single tubular lance having atip end, a butt end, and a head portion, the head portion having acentral main bore at the tip end, having at least one conduit having anorifice at the tip end, and being formed in two parts, an inner blockincluding the central main bore, conduits for fuel gas andcombustion-supporting gas, and respective outlet orifices of the centralmain bore and the at least one conduit, and an outer block includingsupply passageways to the inner block from respective supply tubes forparticulate material and combustion-supporting carrier gas and for fuelgas and combustion-supporting gas; introducing ceramic welding materialscomprised of particulate material containing oxidizable particles andcombustion-supporting carrier gas at the butt end of the single tubularlance, passing the ceramic welding materials and thecombustion-supporting carrier gas through the central main bore and outat the tip end of the single tubular lance during ceramic welding; andconveying a mixture of a fuel gas and a combustion-supporting gasthrough the at least one conduit provided in the head portion other thanthe central main bore during flame treatment, wherein the fuel gas andthe combustion-supporting gas are introduced separately at the butt endof the single tubular lance, are combined in the at least one conduit,and emerge from the tip end to form a flame during flame treatment butnot when the ceramic welding materials are passed.
 14. The process asclaimed in claim 13, wherein the fuel gas is selected from the groupconsisting of propane, acetylene, and acetylene mixtures.
 15. Theprocess as claimed in claim 14, wherein the fuel gas is an acetylenemixture and is tetrene™.
 16. The process as claimed in claim 13, whereinthe combustion-supporting gas is oxygen.
 17. The process as claimed inclaim 13, wherein the fuel gas has a pressure ranging from about 2.0 to2.5 bar (0.2 to 0.25 MPa).
 18. The process as claimed in claim 13,wherein the combustion-supporting gas mixture has a pressure rangingfrom about 4.0 to 5.0 bar (0.4 to 0.5 MPa).
 19. The process as claimedin claim 13, further comprising: applying a flame formed by combustionof the fuel gas to a surface to be treated to achieve a desired effectthereon; stopping the flame by halting the fuel gas supply; andimmediately applying a stream of particles in a combustion-supportingcarrier gas stream the surface to be treated.
 20. The process as claimedin claim 13, wherein no ceramic welding materials are projected duringflame treatment.